TubeNet

Conn and Holton are known to have made/still make short-stroke pistons.

I never heard of York making such valves also until this:

http://tinyurl.com/jr58k

"Kurzhubmaschine" may imply a short-stroke valve block. But the term is not conclusive. And the photo it not really good.

I am not buying, but was asked to sell one of my Eb’s, which I will not do. So I tried to find an alternative.

Klaus Smedegaard Bjerre

It DOES look just like http://www.horn-u-copia.net/picture.php ... rn-u-copia, with the possible exception of some bracing, so I doubt it is a case of a bell being on the wrong horn.

I have never encountered York short-stroke valves, either (although the c.1913 York althorn that I have has hollow, built-up rotary valves to reduce rotating mass, so they obviously knew what they were doing... )